[HayZee518]

if your faucet uses a flare fitting from the supply tube to the faucet itself then no washer is necessary. the brass is harder than the copper supply tube and makes a watertight connection when it is tightened securely. if the top of the supply tube looks sort of flat with a bit of copper sticking out then a cone shaped rubber or hard plastic seal goes here. the gland nut is tightened finger tight then another quarter turn with a bsin wrench.